This is a proposal for a multiphoton laser scanning microscope system. The microscope system consists of 1) a Zeiss 510 NLO multi-photon imaging system with IR capable scanning head and HeNe and Ar lasers for visible light excitation confocal imaging; 2) a Zeiss l00M inverted fluorescence microscope with DIC and high resolution water immersion optics; and 3) a Coherent prechirper (GDC) and a Coherent X-wave optic set for our already existing l0W Ar pumped Coherent Mira 900 femtosecond pulsed Ti:Sapphire laser. The microscope will be placed in an active multi-user facility for examination of single living cells, brain slices, whole embryos and isolated tissues that have been labeled with multiple parameter-indicating fluorescent probes. 2- and 3-photon imaging will minimize photo-damage and photobleaching, maximize penetration into thick specimens, permit excitation of UV-absorbing fluorophores with red and near infrared light, and optimize photon collection efficiency. The new system is sought to relieve the critically high demand for nondestructive imaging of living cells and tissues with high resolution in 3-dimensions. The multiphoton imaging system will complement two conventional laser scanning confocal microscopes already utilized close to capacity. Several investigators will utilize the multiphoton microscope on independent projects in the Departments of Biology, Cell Biology & Anatomy, Medicine, Pediatrics, Pharmacology and Pharmaceutics of the Schools of Medicine and Pharmacy. Multiphoton microscopy will substantially extend our successful and highly productive efforts applying digitized optical microscopy to problems of biology and medicine.